The overall goal of the current proposal is to investigate the cellular and molecular mechanisms of central sensitization that underlies pain hypersensitivity in interstitial cystitis (1C). We previously demonstrated in a somatic pain model (hind paw inflammation) that activation of ERKs (extracellular signal-regulated kinases 1 and 2) and resultant modulation of their downstream target, the Kv4.2 potassium channel, alters neuronal excitability of spinal cord dorsal horn neurons and contributes to central sensitization leading to pain hypersensitivity in somatic pain. Preliminary results in a mouse model of 1C shows that noxious bladder distention in an inflamed bladder also evokes ERK activation in the spinal cord dorsal horn. We therefore hypothesize that pain hypersensitivity of 1C is mediated by dorsal horn pain sensitization involving activation of ERK and involvement of Kv4.2 potassium channels. In our mouse model, cyclophosphamide (CYP) will be used to induce bladder inflammation while phasic bladder distention will be used as a nociceptive stimulus to evoke visceral pain. In SPECIFIC AIM 1, we will test the hypothesis that dorsal horn ERK activation induced by bladder distention in CYP-treated animals is behaviorally relevant. We will perform experiments to test whether ERK activation evoked by bladder distention in CYP-treated mice is associated with nociceptive behaviors and increased abdominal muscle visceromotor response (VMR), an objective measurement of visceral pain. IN SPECIFIC AIM 2, we will test the hypothesis that central sensitization in a visceral pain model of 1C is mediated by activation of MEK-ERK2 signaling. IN SPECIFIC AIM 3, we will test the hypothesis that central sensitization in a visceral pain model of 1C requires the expression of Kv4.2 potassium channels, which are known phosphorylation targets of ERK1/2 in the dorsal horn. These studies will use a combination of molecular and behavioral techniques to elucidate mechanisms involved in spinal central sensitization leading to pain hypersensitivity in 1C. We have extensive experience in the biochemical and behavioral approaches and a unique set of knockout and transgenic animals (MEKdn, ERK1-/-, Kv4.2-/-) to carry out the proposed experiments. The spinal cord is a new frontier in 1C pain research. A better understanding of the mechanisms of pain sensitization in 1C may open up new therapeutic paradigms that target the central nervous system in a chronic visceral pain syndrome like 1C.